The heart of a computer's long term memory is an assembly that is referred to as a magnetic hard disk drive. The magnetic hard disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head can include a coil that passes through a magnetic yoke that includes a write pole located between leading and trailing return poles. Current conducted to the coil layer induces a magnetic flux in the pole pieces which causes a write field to emit from the write pole for the purpose of writing a magnetic transition in tracks on the moving media, such as in circular tracks on the rotating disk. The write field passes through a magnetically soft under-layer of the magnetic media and returns to the return poles where it is sufficiently spread out and weak that it does not erase the previously recorded bit.
In the quest for every increased data capacity and data rate, researchers have sought means for improving the performance of such magnetic write heads. Such an increase in performance can include maximizing the write field strength as well as minimizing the time necessary to switch the magnetic polarization of the poles of the magnetic write head (e.g. maximizing switching speed).